How to Map Response object returned by Http Service to a TypeScript Objects using Observable Map function in Angular2

问题

Hi I have created an angular2 service whose task is to call a webapi which returns data in a json object structure as follows:

//Result of the webapi service call.
{
  "Total":11,
  "Data":[{"Id":1,"Name":"A","StartDate":"2016-01-01T00:00:00"},
     {"Id":2,"Name":"B","StartDate":"2016-02-01T00:00:00"}]
}

Here is my angular2 service. The getMileStones methods work perfectly and I am able to cast the response back to MileStone[] . But In order to get the paged data I have created a function getPagedMileStones(int,int) which call a webapi method and return the result as mentioned above structure .I want to cast the returned response from webapi to IPagedResponse. But I am not able to make it work properly. I have an Interface IPagedResponse and I want this function to return this information back to the component calling so that I can provide paging functionality.

    import { MileStoneModel} from './milestoneModel'
    import { Http, Response, Headers, RequestOptions } from '@angular/http'
    import { Injectable } from '@angular/core'
    import { Observable }     from 'rxjs/Observable';

    import {PaginatePipe, PaginationService, PaginationControlsCmp, IPaginationInstance} from 'ng2-pagination';
    import 'rxjs/Rx';

    export interface IPagedResponse<T> {
        total: number;
        data: T[];
    }

    export interface DataModel {
        id: number;
        data: string;
    }

    @Injectable()
    export class MileStoneService //implements IPagedResponse<MileStoneModel>
    {

        data: MileStoneModel[];
        //private _page: number = 1;
         total: number;

        private pagedResult:  IPagedResponse<MileStoneModel>;

        mileStones: MileStoneModel[]
        private url: string = "http://localhost/ControlSubmissionApi/api/Milestones";
        constructor(private http: Http) {


        }
        getMilestones(): Observable< MileStoneModel[]> {

            return this.http.get(this.url)
                .map((response: Response) => <MileStoneModel[]>response.json())            
                .catch(this.handleError);


        }
        //----------- Starts here -------------
        getTypedPagedMilestones(page: number, pageSize: number) {
            debugger;
            return this.http.get(this.url + "/" + page + "/" + pageSize)
                .map((res: Response) => { this.data = <MileStoneModel[]>res.json().Data; this.total = res.json().Total; })
                //.map((Data, Total) => { console.log(Data); console.log(Total); })
                .catch(this.handleError);
        //----------- Ends here ------------

        }

        getMilestone(id: number):Observable< MileStoneModel> {

            return this.http.get(this.url+"/"+id)
                .map((response: Response) => <MileStoneModel>response.json())
                .catch(this.handleError);

        }
        searchMileStones(name: string): Observable<MileStoneModel[]> {
            let headers = new Headers({ 'Content-Type': 'application/json' });
            let options = new RequestOptions({ headers: headers });
            return this.http.get(this.url+"/search/"+name)
                .map((response: Response) => <MileStoneModel[]>response.json())
                .catch(this.handleError);
        }
        addMileStone(formdata:string) {
            //let body = JSON.stringify({ newMileStone });
            let headers = new Headers({ 'Content-Type': 'application/json' });
            let options = new RequestOptions({ headers: headers });

            return this.http.post(this.url, formdata, options)
                .map((response: Response) => <MileStoneModel>response.json())        
                .catch(this.handleError);

        }
        private handleError(error: any) {
            // In a real world app, we might use a remote logging infrastructure
            // We'd also dig deeper into the error to get a better message
            let errMsg = (error.message) ? error.message :
                error.status ? `${error.status} - ${error.statusText}` : 'Server error';
            console.log(errMsg); // log to console instead
            return Observable.throw(errMsg);
        }
    }

回答1:

Wouldn't this work? I don't see any variable on your code that is a type of IPagedResponse

    pageResponse: IPagedResponse<MileStoneModel>;

    getTypedPagedMilstones(page: number, pageSize: number): Observable<IPagedResponse<MileStoneModel>> {
        return this.http.get(this.url + "/" + "/" + pageSize)
            .map((res: Response) => {
                this.pageResponse.data = <MileStoneModel[]>res.json();
                this.pageResponse.total = res.json().Total;
            })
            .catch(this.handleError);
    }

回答2:

getPagedMilestones(page: number, pageSize: number): Observable<IPagedResponse<MileStoneModel>> {

    return this.http.get(this.url + "/" + page + "/" + pageSize)
        .map((response: Response) => {
            return {
                data: <MileStoneModel[]>response.json().Data,
                total: response.json().Total
            }
        })
        .catch(this.handleError);
}

来源：https://stackoverflow.com/questions/40347814/how-to-map-response-object-returned-by-http-service-to-a-typescript-objects-usin